Latin name of the genus and species claimed: Vitis vinifera. 
Variety denominations: xe2x80x98Sugratwentyeightxe2x80x99.
This invention relates to the discovery and asexual propagation of a new variety of grapevine as herein described and illustrated. The new variety was first hybridized by David W. Cain and Michael J. Striem in Kern County, Calif. The new variety xe2x80x98Sugratwentyeightxe2x80x99 is characterized by possessing naturally large, round, seedless grapes. The grapes have a black tough and tannin skin, with medium sugar content, and medium acidity, resulting in a good eating quality. The grapes ripen mid-season, approximately a week before xe2x80x98Redglobexe2x80x99 (unpatented) and about 3-4 weeks after xe2x80x98Thompson seedlessxe2x80x99 (unpatented) grape, when grown in the San Joaquin Valley, Calif.
The new variety was created by hybridization of two xe2x80x9cseedlessxe2x80x9d grapes possessing small, abortive, vestigial ovules. From the initial population of hybrid ovules, embryo rescue procedures were used to produce a population from which the present variety was selected. The seed parent is xe2x80x98Sun World Seedling 89145-062-244xe2x80x99 (unpatented) variety and the pollen parent is xe2x80x98Sun World Seedling 89014-019-280xe2x80x99 (unpatented). The parent varieties were first crossed in May 1992, with the date of sowing being August 1992, and the date of first flowering being May 1994. The new xe2x80x98Sugratwentyeightxe2x80x99 variety was first asexually propagated by David W. Cain in January, 1995, in Wasco, Kern County, Calif., using hardwood cuttings.
The new variety xe2x80x98Sugratwentyeightxe2x80x99 is distinguishable from its seed parent xe2x80x98Sun World Seedling 89145-062-244xe2x80x99 by having a much smaller and softer seed trace. Additionally, the berry skin color of xe2x80x98Sugratwentyeightxe2x80x99 is much darker than the berry skin color of its seed-parent. The pollen parent xe2x80x98Sun World Seedling 88014-019-280xe2x80x99 tends to develop many shot berries, and the large berries are much softer than those of xe2x80x98Sugratwentyeightxe2x80x99.
The new variety xe2x80x98Sugratwentyeightxe2x80x99 most nearly resembles the xe2x80x98Sugrasixteenxe2x80x99 variety U.S. Plant Pat. No. 11,749) in its berry skin color and ripening time. It can be distinguished from xe2x80x98Sugrasixteenxe2x80x99 by possessing round grapes with firm and juicy flesh, along with a tough skin having a tannin flavor. Additionally, the vine of the new variety xe2x80x98Sugratwentyeightxe2x80x99 is less vigorous and less productive than the vine of xe2x80x98Sugrasixteenxe2x80x99. It also differs from xe2x80x98Sugrasixteenxe2x80x99 by having naturally larger and round berries, with much heavier bloom on the berry skin.
The new grapevine variety xe2x80x98Sugratwentyeightxe2x80x99 also resembles the xe2x80x98Redglobexe2x80x99 grapevine variety by possessing large, rounded grapes. It can be distinguished from the xe2x80x98Redglobexe2x80x99 variety by being seedless and by ripening about one week earlier than xe2x80x98Redglobexe2x80x99. The new grapevine variety can be further distinguished from xe2x80x98Redglobexe2x80x99 by having a black berry color, and tough, tannic skin.
The new xe2x80x98Sugratwentyeightxe2x80x99 variety has been shown to maintain its distinguishing characteristics through successive asexual propagations by, for example, cuttings.